1. Field of the Invention
The present invention relates to a method and apparatus for producing a raw edge belt.
2. Description of the Related Art
A raw edge belt is a ring-shaped power transmission belt a section of which is an inverted trapezoid (or V-form). FIG. 3 is a perspective view of a belt showing a section and part thereof. As shown in FIG. 3, the belt is provided with an upper rubber layer 31, tensile members 32, and a lower rubber layer 33. FIG. 4 shows the production procedure of a belt. The production procedure is 1) to build these constituent materials, in this order, as cylindrical layers, starting from the inner side, then vulcanize the built-up work to form a sleeve (vulcanized sleeve, of which section is shown in FIG. 4 (a)); 2) to slice or section the sleeve into pieces of a desired width (belt width) along the dotted lines x to get ring-shaped belts of which section is rectangular (called square-cut belts and shown in FIG. 4 (b)); and 3) to cut these square-cut belts obliquely along the dotted lines y to get raw edge belts of which section is a V-form (FIG. 4 (c)). The present invention relates to steps for cutting the square-cut belts into belts of a V-form section to get raw edge belts.
For example, examined Japanese Provisional Patent Publication No. HEI 5-28978 discloses "a production method wherein a vulcanized sleeve is put between two spindles, the sleeve is made to run circularly, a group of integrated grinding wheels, comprising a plurality of grindstone discs of which peripheral section is a V-form, is kept rotated and pressed against the peripheral surface of the vulcanized sleeve to cut into it and grind plural V-shaped grooves, and positioning members are fit into the V-grooves to cut the sleeve into individual raw edge V-belts."
Another method for producing a raw edge V-belt is, first, to square-cut (this means slicing or sectioning a sleeve into rings having a rectangular section) a vulcanized sleeve into pieces of a desired belt width, then to grind and polish a belt, one at a time, to change its section into a V-form. As for a production apparatus for grinding a belt into a V-section belt, Japanese Provisional Patent Publication No. HEI 8-164568 discloses a V-section cutting apparatus wherein two milling cutters are arranged so that their cutting edges have angles of inclination for grinding the sides of a belt into a V-section.
The method disclosed by the above-mentioned Japanese Patent Publication No. HEI 5-28978 tends to induce meandering since a wide vulcanized sleeve is made to run circularly over two spindles. Moreover, as many grinding wheels are made to cut into the sleeve concurrently to form V-grooves, the sectional configuration may be distorted by compression, resulting in defective configurations (dents in the inclined sides or displacement). As for the method wherein one square-cut belt is polished into a V-section belt at a time, the productivity is low, resulting in higher cost. As for the milling system with cutters, the life of the cutters is short, posing problems of cutter replacement time and higher cost.
The present invention is intended to solve the above-mentioned quality problems caused by meandering, displacement, etc., and at the same time, to solve the problems of longer working time and higher cost of the method of finishing one square-cut belt at a time.